Second example for @State property wrapper.

ContentView.swift

import SwiftUI

struct ContentView: View {
    
    @State private var nameString : String?
    
    var nameArray : [String] = ["Giray","Eren","Feyza","Can","Emre","Mehmet","Buse"]
    
    var body: some View {
        VStack {
            Text(nameString ?? "No name")
            Button("Change text") {
                nameString = getRandomElement(from: nameArray)
            }
        }
    }
    
    func getRandomElement(from array: [String]) -> String {
        return array.randomElement() ?? "No name"
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}